NI 5112 Electromechanical Relays

NI High-Speed Digitizers Help (NI-SCOPE)

Edition Date: January 2017

Part Number: 370592AB-01

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The NI 5112 contains electromechanical relays that have life spans of 1–2 million operations. To prolong the life of these relays, and subsequently the life of the digitizer, consider the following programming practices.

Small modifications to your NI-SCOPE application can significantly minimize the number of relay operations. For example, you can avoid unnecessary resets, frequent changes to specific vertical parameters, and excessive self-calibration, all of which can cause the relays to switch.

Resetting the digitizer by calling niScope Reset or by calling niScope Initialize with the reset parameter enabled restores the default properties of the device, which subsequently switches the relays. This type of reset is known as a software reset. Theoretically, you may never need to call reset if you always know the current state of the device. Consider the following two strategies for managing the state information for the device:

  • In the first strategy, you can manage state information programmatically by updating the current configuration properties in a LabVIEW cluster or C structure, for example. This method would allow you access to the current configuration at any time and prevent a situation where the program has no knowledge of the current configuration. Because the reset brings the device back into a known state, it would be unnecessary to call reset because you have already maintained this state information programmatically. You can then use the same instrument session throughout the program.
  • In the second strategy, you close the session and create a new session whenever you would otherwise reset the device. You create a new session by calling the niScope_Initialize VI or the niScope_init function with reset disabled. You close the session by calling niScope Close VI or the niScope_close function. Each time you create a new session, you implement a pseudo reset of the parameters. The configuration changes are not actually made at this time and no relay operations occur. After you have defined any other parameters such as vertical or channel configuration properties, the configuration changes appropriately. Using this method, you can avoid calling the device reset and the relays switch only when necessary.

Certain property changes affect the relays. Changing the vertical range across the 0.5 V and 5 V levels is the most common cause of relay changes. Enabling and disabling channels also switches the relays. Other less frequent operations include changing input impedance and performing self-calibration. Consider the order of your test operations if you find you are changing these vertical parameters more than necessary.

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